/**
 * A plugin which enables rendering of math equations inside
 * of reveal.js slides. Essentially a thin wrapper for MathJax.
 *
 * @author Hakim El Hattab
 */
var RevealMath = window.RevealMath || (function () {

    var options = Reveal.getConfig().math || {};
    options.mathjax = options.mathjax || 'https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.0/MathJax.js';
    options.config = options.config || 'TeX-AMS_HTML-full';

    loadScript(options.mathjax + '?config=' + options.config, function () {

        MathJax.Hub.Config({
            messageStyle: 'none',
            tex2jax: {
                inlineMath: [['$', '$'], ['\\(', '\\)']],
                skipTags: ['script', 'noscript', 'style', 'textarea', 'pre']
            },
            skipStartupTypeset: true
        });

        // Typeset followed by an immediate reveal.js layout since
        // the typesetting process could affect slide height
        MathJax.Hub.Queue(['Typeset', MathJax.Hub]);
        MathJax.Hub.Queue(Reveal.layout);

        // Reprocess equations in slides when they turn visible
        Reveal.addEventListener('slidechanged', function (event) {

            MathJax.Hub.Queue(['Typeset', MathJax.Hub, event.currentSlide]);

        });

    });

    function loadScript(url, callback) {

        var head = document.querySelector('head');
        var script = document.createElement('script');
        script.type = 'text/javascript';
        script.src = url;

        // Wrapper for callback to make sure it only fires once
        var finish = function () {
            if (typeof callback === 'function') {
                callback.call();
                callback = null;
            }
        }

        script.onload = finish;

        // IE
        script.onreadystatechange = function () {
            if (this.readyState === 'loaded') {
                finish();
            }
        }

        // Normal browsers
        head.appendChild(script);

    }

})();
